c# - 基于书籍构建 LINQ 查询

Question

(这个问题的标题不是最好的，但我不确定该怎么说!)

我正在处理包含值 list 的搜索表单。基本上，选中的项目意味着“在搜索中包含此类型”。像这样:

Search for item: __________
Search in:
      [ ] Fresh Foods
      [ ] Frozen Foods
      [ ] Beverages
      [ ] Deli Counter

我有一个对象来表示这个搜索:

class FoodSearchCriteria{
    public string SearchString {get;set;}
    public bool SearchFreshFoods {get;set;}
    public bool SearchFrozenFoods {get;set;}
    public bool SearchBeverages {get;set;}
    public bool SearchDeliCounter {get;set;}
}

我能想到做这个 atm 的唯一方法是这样的:

public IList<FoodItem> FindFoodItems(FoodSearchCriteria criteria)
// in reality, this is a fuzzy search not an exact match
var matches = _DB.FoodItems.Where(x => x.FoodTitle == SearchString);

var inCategories = new List<FoodItem>();

if (criteria.SearchFreshFoods)
   inCategories.Add(matches.Where(x => x.Type == 'Fresh Foods'));
if (criteria.SearchFrozenFoods)
   inCategories.Add(matches.Where(x => x.Type == 'Frozen Foods'));
//etc etc

return inCategories;
}

这对我来说感觉像是一种代码味道，有什么更好的方法来处理它？<​​/p>

Answer 1

看看PredicateBuilder

PredicateBuilder predicate = PredicateBuilder.False<FoodItem>();
if (criteria.SearchFreshFoods)
{
    predicate = predicate.Or(x => x.Type == 'Fresh Foods');
}
if (criteria.SearchFrozenFoods)
{
    predicate = predicate.Or(x => x.Type == 'Frozen Foods'));
}
...

_DB.FoodItems.Where(predicate);